If you don't exercise regularly and vigorously, expect to lose a significant amount of muscle strength as you age, and expect that loss of strength to reduce the quality of your life. A 15-year follow-up study showed that older people who lift weights at least twice a week had a 46 percent lower death rate within the study period, a 41 percent lower death rate from heart attacks, and a 19 percent lower death rate from cancer, compared to the control group that did not lift weights (Preventive Medicine, June 2016;87:121-127).

• In one study, older people with the highest loss of muscle strength were four times more likely to be disabled, have difficulty walking and need walkers or other mechanical devices to help them walk (Am J Epidemiol, 1998; 147(8):755–763). The authors of this study said, “Exercise decreases body fat and obesity, increases muscle strength, improves balance, gait, and mobility, decreases likelihood of falling, improves psychological health and reduces arthritis pain, heart attacks, osteoporosis, cancer and diabetes."

• Just eight weeks of lifting weights increased muscle strength in a group of men 80 to 88 years old (Aging Clin Exp Res, April 2010;22(2):134-40).

Exercise Reduces Loss of Muscle
Muscles are made up of thousands of individual muscle fibers. Each muscle fiber is innervated by a single nerve. With aging, humans lose the nerves that innervate muscle fibers and with each nerve loss, they lose the associated muscle fiber. For example, the vastus medialis muscle in the front of your thigh contains approximately 800,000 muscle fibers when you are 20 years old, but by age 60, it will have only about 250,000 fibers. The average person loses about eight percent of muscle size in the decade between 40 and 50 years of age, and the rate of loss increases to 15 percent per decade after age 75 (J Am Geriatr Soc, March 2003;51(3):323-30). You can slow the loss of muscle fibers as you age and can enlarge the remaining muscle fibers by exercising against resistance, but you cannot increase the number of fibers once they are lost (The Journals of Gerontology, August 2012).

Resistance exercise increases muscle size and strength in older people (Med. Sci. Sports Exerc, 2011; 43 (2): 249–58), but with aging you need to work much harder to gain the amount of strength that a younger person would get with the same program. In older people, resistance training can enlarge the remaining muscle fibers, but it does not increase the number of fibers in a muscle (Med Sci Sports Exerc, July 2011;43(7):1177-87).

How to Grow Larger Muscles As You Age
The stimulus to enlarge a muscle is to exercise against resistance vigorously enough to damage your muscles. Muscles grow when they heal from muscle damage. You can tell that you are causing muscle damage because of the burning you will feel in muscles when you are exercising and the delayed onset muscle soreness (DOMS) that you feel 8 to 24 hours after you finish exercising. Then you take easier workouts until the soreness goes away, usually in 24 to 48 hours. If you take hard workouts when muscles are sore, you are likely to tear them and not be able to exercise again until your injuries heal.

Taking in extra protein without doing resistance exercise will not increase muscle size or strength; see my report on Extra Protein Does Not Enlarge Muscles. However, eating foods that contain both protein and carbohydrates after a workout can help muscles to heal faster and grow stronger.

Lifting Lighter Weights with More Repetitions
In one study, older men gained more muscle strength by spending more time lifting lighter weights, whereas younger men gained more muscle strength by lifting heavier weights. In younger men, doubling exercise volume by spending more time lifting weights produced limited added muscle enlargement. In older men, it resulted in much larger muscles and far more strength (The Journals of Gerontology, August 2012).

Exercising as You Age Keeps More Fast-Twitch Fibers
Muscles are made up primarily of two types of fibers: fast twitch fibers that govern strength and speed, and slow twitch fibers that govern endurance. Inactivity causes a far greater loss of the fast twitch muscle fibers that govern strength and speed (J Cell Mol Med, Sep 2009;13(9B):3032-50), so exercise makes you stronger by causing your muscles to retain more fast twitch fibers.

Benefits of Life-long Exercise
Inactivity at any age causes tremendous loss of muscle size and strength. If you inactivate a leg by putting it in a cast, you lose a large amount of muscle size in just four days. However, if you make the inactivated leg muscles contract by stimulating them with an electric current, some of the loss of muscle size is prevented (Nutrition, Acta Physiol (Oxf), March 2014; 210(3):628-41).

Life-long competitive athletes over 50 who train four to five times per week do not lose as many of the nerves that innervate muscles, so they retain more muscle size and strength with aging (The Physician and Sportsmedicine, Sept 2011;39(3):172-8). Other studies show that life-long competitive runners over 60 had almost the same number of muscle fibers as 25-year-olds. If you are not a life-long exerciser, there is still plenty of benefit from exercise no matter when you start.

Join a Gym
First check with your doctor to make sure you do not have any condition that will be harmed by vigorous exercise. Then join a gym and ask for instructions on how to use the weight-training machines. As a general rule, on each machine, you will try to move a weight 10 times in a row, rest a minute, and then do two more sets of 10. In the beginning, you should lift very light weights and go home without sore muscles. After a few weeks of lifting weights three times a week, not on consecutive days, you can gradually try to add more weight on your machines. Older people are at increased risk for injuries, so always stop a lifting workout when you feel pain in one spot that worsens as you continue to lift a weight.

About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities.
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